Stress cracking susceptibility during drying process of two varieties of Khazar (Long-grain), and Hashemi (longer-grain) rice was investigated. Thin-layer drying tests were conducted with air drying temperatures of 35°C, 45°C, 55°C and 65°C. Stress-cracking development reactions in the endosperm of rice kernels was investigated during drying with various temperatures of drying air and in passing from moisture contents of 18%, 15% and 12%(w.b.). Stress-cracking index (SCI) was applied to quantify stress cracking susceptibility (severity of damage to endosperm) induced to kernels by drying. The drying air temperature and the removal of moisture content have important effects on the development of stress cracking. For Hashemi variety, from 45°C on, and for Khazar variety a moment lower than that (by increase in temperature), SCI increased intensively. To attain the moisture content of 15%(w.b.), either of the varieties could be dried with higher temperatures without inducing any high SCI. Air drying temperatures of 55°C for Hashemi variety and a moment higher than 45°C for Khazar variety were recommended, Then the drying process should continue with the lowest possible temperature. Khazar (long-grain) variety was more susceptible to fissuring than Hashemi (longer-grain).
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